Windows only: Free utility CrystalDiskInfo keeps tabs on your hard drive health, including temperature, S.M.A.R.T. disk reporting, and the number of power cycles and run time on each disk. Although there is no silver bullet that can predict hard drive failure, if you're paranoid about your data you might factor in how many hours a disk has been running to determine its replacement schedule. Knowing that one of your disks has had two solid years of uptime (like my primary operating system disk has) might encourage you to rotate it into retirement after that. CrystalDiskInfo is a free download for Windows only.